Logical Reasoning

PT119 · S3 · Q25 False chicory’s taproot is always

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False chicory’s taproot is always one half as long as the plant is tall.

Statements

conditional / mathy (always / 1/2 as long) False chicory’s taproot is always 1/2 as long as it is tall.

volume dial (the more x, the more y) The more rain FC gets, the taller it tends to grow.

conditional (always) FC receives more above average than twice the average → height for FC rain for that habitat

Evaluate

This is a bit of a mess. We have a conditional in the last sentence, but we don't have any other conditionals to chain it up with or any facts that would trigger it (or its contrapositive).

The middle idea is almost a Volume Dial relationship, but it is hedged with the language "tend to". More rain tends to go with taller FC's. Since this is a Must Be True question, whereas that statement doesn't present a must be true idea, the correct answer probably won't lean on that 2nd claim.

The Overlapping Information is "false chicory / rain / tallness". The 2nd and 3rd claims are basically stressing that with rain, the FC gets taller.

And the 1st claim is saying the taproot is always 1/2 of the tallness. So I guess we could say that, "as it rains, the taproot gets longer".

Goal

Find something we can prove, possibly connecting the idea of rain to how long the taproot is.

25.

If the statements above are true, then which one of the following must also be true?

  1. If two false chicory plants

    Too Strong: likely

    This conditional has a Trigger we know very little about. If we have two FC plants that are different heights, would any of these 3 claims be applicable? Claim 1 would. If two FC plants are different heights, then their taproots are of different lengths. Claim 2 would not. We couldn't assume that the taller one has received more rain. Sure "more rain tends to mean taller", but it could also be true that, "the better the soil, the taller it grows" or "the more you sing to it, the taller it grows". Claim 3 would not. This doesn't have anything to do with comparing two FC's that different in height. It only has to do with FC's that are above-average height vs. not above-average height. So this trigger, "two FC's are different in height" would only allow us to derive a must be true that "their taproots are different in length", whereas the outcome of this answer choice's conditional is talking about "likely is received less than twice the average rain". We can't prove that. It's possible that the two FC plants we're comparing are both above-average height and have both received more than twice the average rainfall. Two super tall plants can still differ in height.

    4% picked this

  2. If a false chicory plant

    Reversed Logic

    We could sign off on the idea that if a false chicory plant has received more than twice the average rainfall, then it will have a longer-than-average taproot. After all, false chicory's that receive that much rain are always above average height, and taproot length is just 1/2 of height. But we can't make this move backwards. After all, getting twice as much rain is only presented as one sufficient cause of above-average height. There might be other things that cause a false chicory plant to be above-average height (e.g. treated with soil fertilizer). Perhaps the majority of tall FC's got that way from fertilizer, not from tons of rain. That would make this conditional false. A longer-than-average taproot more more likely be an indication of fertilizer, not tons of rain.

    15% picked this

  3. It is not possible for

    Too Strong: not possible Negated Logic

    We were told does get more than ? will be above twice average rain average height This answer is selling an illegal negation of that does not get more ? will not be above than twice average rain average height There might be other ways that FC plants can grow to be above-average height (such as applying fertilizer to their soil). Receiving tons of rainfall was sufficient to make FC plants taller. It wasn't necessary.

    3% picked this

  4. If the plants in one

    Too Strong: must be same

    The contrapositive of this rule says this: two groups of FC one group of FC plants received ? will be taller than non-identical the other group amounts of rainfall Can we derive something that harsh? Any time there's a difference in rainfall there will be a difference in height? No, that's too strong. The 2nd sentence only said that the more rain received, the taller the plant tends to grow. That doesn't guarantee that "more rain = taller". Also, more than one thing can potentially affect growth. You might have one group of FC plants receive more rain, but the other group receives more sunlight and soil nutrients, and thus they end up the same height as each other.

    3% picked this

  5. Correct

    If a false chicory plant

    Why this is right

    This is connecting rainfall to length of taproot, as we anticipated, but, unlike (B), the conditional logic matches. The trigger here (receiving lots of rain) matches the trigger in the 3rd claim. The 3rd claim tells us that if an FC receives more than 2x avg rain, it will always be above-average height. Let's say average height is 20 inches, so this FC plant that received all that rain is now 24 inches. The 1st claim tells that the taproot's length is always 1/2 of the plant's height. So an average height FC plant would have a 10 inch taproot and an above-average FC plant would have a 12 inch taproot. So, yes, if that much rain guarantees above-average height, and taproot is always half of height, then that much rain guarantees above-average taproot.

    Skill tested: Must be True · how this choice captures the argument's function is the move to repeat next time.

    75% picked this

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